1. Field of the Invention
This invention relates to the recovery of purified ditertiary butyl peroxide from a feedstock containing a minor amount of ditertiary butyl peroxide. More particularly, this invention relates to a method for the recovery and purification of ditertiary butyl peroxide from a feedstock comprising a major amount of tertiary butyl alcohol and only a minor amount of ditertiary butyl peroxide. Still more particularly, this invention relates to a method wherein ditertiary butyl hydroperoxide is recovered from a feedstock obtained by the oxidation of isobutane to provide a reaction mixture comprising unreacted isobutane, tertiary butyl alcohol, tertiary butyl hydroperoxide and a minor amount of ditertiary butyl peroxide or a reaction mixture obtained by the epoxidation of propylene with tertiary butyl hydroperoxide to propylene oxide and comprising propylene, propylene oxide, tertiary butyl alcohol, unreacted tertiary butyl hydroperoxide, ditertiary butyl peroxide, acetone and other contaminants.
2. Prior Art
It is known to react oxygen with isobutane to form a peroxidation reaction product wherein the principal peroxide that is formed is tertiary butyl hydroperoxide. However, a minor constituent of such a reaction product is ditertiary butyl peroxide, which is a valuable commercial product used, for example, as a high temperature free radical initiator in chemical reactions.
Conventionally, ditertiary butyl peroxide is prepared by the reaction of tertiary butyl alcohol or isobutylene with tertiary butyl hydroperoxide in the presence of an acid catalyst.
The coproduction of propylene oxide together with another hydrocarbon, such as tertiary butyl alcohol, is summarized in an article "Propylene Oxide by the Coproduct Process" by Landau et al. (Chem. Tech., October 1979, pp. 602-607).
The process is described in greater detail in Kollar U.S. Pat. Nos. 3,350,422 and 3,351,635 which are directed to the catalytic epoxidation of an olefin by reaction with a hydroperoxide such as tertiary butyl hydroperoxide. When the olefin is propylene and the hydroperoxide is tertiary butyl hydroperoxide, the principal reaction products are propylene oxide and tertiary butyl alcohol.
Herzog U.S. Pat. No. 3,928,393 is directed to an improvement in the Kollar et al. process wherein citric acid is used to minimize iron catalyzed decomposition of the organic hydroperoxide. This patent includes examples directed to the preparation of tertiary butyl hydroperoxide by the reaction of isobutane with oxygen.
Grane U.S. Pat. No. 3,474,151 is also directed to the oxidation of isobutane with oxygen to provide tertiary butyl alcohol and discloses that the reaction mixture contains not only tertiary butyl hydroperoxide, but also ditertiary butyl peroxide. In their U.S. Pat. No. 4,239,926, Grane et al. disclose a method for significantly drying the tertiary butyl alcohol prepared by the oxidation of isobutane, the method involving extractive distillation of the tertiary butyl alcohol product using a specially proportioned blend of xylene, acetone and water as the extractant.
Harvey U.S. Pat. No. 3,449,217 is directed to a method for the recovery of tertiary butyl hydroperoxide from a mixture of tertiary butyl hydroperoxide and tertiary butyl alcohol. However, nothing is said in the patent about the recovery and purification of the ditertiary butyl peroxide.